You can use Scrutinizer (free for Open Source projects) or SensioLab Insight (from those guys of Symfony and Twig, free -> limited version) or CodeClimate (free for Open SOurce projects) for that, directly in your GitHub repo.

Here you can see a comparison, instead, between Code Climate vs. Scrutinizer vs. SensioLabsInsight.

I've been using Visual Studio Code for several weeks now and I find it a pleasure to use. Even it's from Microsoft, it's open source, free and available on all platforms (My OS is Ubuntu) It's part of their charm offensive, "we're not so bad after all". There is some integration with git, which is nice.